Stacked stator core and method of manufacturing thereof, and rotary motor and method of manufacturing thereof

ABSTRACT

The present invention relates to a structure of a stacked stator core formed when rotary motors are manufactured and to a method of manufacturing the stacked stator core. It is possible to improve the workability in the winding process and the productivity of the stator and the rotary motor because the stacked stator core includes a plurality of stator cores  300 , each of which is made up of a prescribed number of stacked sheet magnetic materials, a plurality of yoke members  301  forming each stator core, a bendable bent portion  304  provided between the yoke members, and an interconnecting portion  401  for connecting the plurality of stator cores  300  one another while providing a difference in level, by connecting the top end of one stator core with the bottom end of the other stator core.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotary motor and a stator used fordriving a medium used in a magnetic disk drive unit, optical disk driveunit or the like. More particularly, the present invention relates tothe structure of the rotary motor and the stator in order to improve themass productivity and to a method of manufacturing thereof.

2. Description of Related Art

A conventional rotary motor stator of this type (not shown) manufacturedby stacking a plurality of ring-shaped board members blanking directlyfrom a steel board, as disclosed in JP-A-100823/1982, for instance.However, yield of materials is low. For this reason, JP-B-46620/1985discloses the improved yield by winding a belt-shaped board member witha large number of teeth in spiral while plastically deforming the boardmember to fasten a several layers by welding the respective layers.

As an another conventional method of manufacturing the rotary motor,there is a method disclosed in JP-A-98774/1999. FIGS. 48 and 49 are aview showing such a method.

Referring to FIGS. 48 and 49, the method involves feeding a strip-shapedmagnetic material 500 to a press machine 502 through a work feedingmachine 501, forming a core member 503 consists of thinned portions 503a, yoke members 503 b, and magnetic pole teeth 503 c, formingring-shaped stacked yoke members 505 by winding a reel 504 by aplurality of turns such that the core member 503 corresponding to aplurality of stator cores are arranged during one turn, winding drivingcoils 506, dividing ring-shaped stacked yoke member 505 into blocks suchthat a stator core 507 corresponding to one rotary motor is provided,and producing stators for rotary motors by bending the stator core 507with a tool.

The conventional rotary motor stators are constructed as above. Thus,the stator disclosed in JP-A-100823/1982 has not only the low yield ofmaterials as mentioned above, but also is heavy to assemble thereof asthe assembly forces a great number of the board members to be graspedone by one for conveyance. The stator disclosed in JP-B-46620/1985 has adifficulty in unfolding and dividing the stators for winding as thebelt-shaped board member is wound up in spiral while plasticallydeforming. Regardless, they lack productivity.

Moreover, the method of manufacturing rotary motors disclosed inJP-A-98774/1999 has also the following problems.

(1) The diameter of connected stator cores 507 is very large comparedwith the thickness of stacked yoke member 505 for the reason that statorcores 507 corresponding to a plurality of rotary motors are connected inthe circumferential direction. Therefore, the stacked yoke members 505are apt to sag, which makes worse handling of stacked yoke members 505in coating them with insulation coating and placing them onto thewinding machine.

(2) It is difficult to provide a positioning portion for mounting thestator core 507 on the rotary motor and a stator-connecting for formingthe stator core 507 in a ring and holding it for the reason that theyoke members having the same shape are continuously produced and theyare wound up.

(3) The magnetic pole teeth 503 c are stacked on the slant for thereason that the strip-shaped magnetic material 500 is provided with yokemembers and the strip-shaped magnetic material 500 is wound up in aspiral form around a reel to form stacked yoke members 505. As a result,this incurs the deteriorated productivity in the winding process, andthe decreased driving torque of the rotary motor and the torque ripplethereof.

The present invention has been made to solve the above problems. Anobject of the invention is to provide a stacked stator core capable ofimproving the workability in the winding process and the productivity ofthe product and a method of manufacturing the stator, and a rotary motorequipped with the stator and a method of manufacturing the rotary motor.

SUMMARY OF THE INVENTION

The stacked stator core to according to the present invention includes afirst core member formed by stacking a prescribed number of magneticmaterials and made up of a plurality of yoke members connected to oneanother through a bendable bent portion; a second core member formed bystacking the prescribed number of magnetic materials and made up of ayoke member arranged in such a manner that one end of each magneticmaterial of the second core member is successively connected to theother end of the first core member through a bendable bent portion fromthe next magnetic material of the other end of the first core member byshifting entirely the second core member downwards, with left the samenumber of stages of one end of the second core member unconnected as theprescribed number of stages; a third core member formed by stacking theprescribed number of magnetic materials, each of which is made up of thesame number of yoke members as the first core member connected throughthe bendable bent portion, and one end of the magnetic material of thethird core member is connected to the other end of the second coremember through a bendable bent portion by shifting entirely the thirdcore member downwards; and a fourth core member formed by stacking theprescribed number of magnetic materials and made up of a yoke memberarranged in such a manner that one end of each magnetic material of thefourth core member is successively connected to the next stage of theother end of the third core member through a bendable bent portion fromthe next magnetic material of the other end of the third core member byshifting entirely the fourth core member downwards, with left the samenumber of stages of one end of the fourth core member unconnected as theprescribed number of sages; wherein the first, the second, the third andthe fourth core members are independently arranged in a ring andmutually stacked.

This provides a stacked stator core able to easily unfold and dividewinding.

The method of manufacturing a stator according to the present invention,includes the steps of forming the stacked stator core by blanking amagnetic material of claim 1 using a progressive die; unfolding thestacked stator core straight; subjecting the straight stacked statorcore to a prescribed treatment; winding a wire around the straightstacked stator core subjected to the prescribed treatment; and windingup the straight wire-wound stacked stator core to restore the core toits original arrangement in a ring.

This provides a method of manufacturing a stator able to improve theworkability in the winding process and the mass productivity.

The method of manufacturing a stacked stator core according to thepresent invention includes a plurality of stator cores, each of which ismade up of a prescribed number of stacked sheet magnetic materials; aplurality of yoke members forming each stator core; a bendable bentportion provided between the yoke members; and an interconnectingportion for interconnecting the plurality of stator cores by connectingthe upper end of one stator core to the lower end of the other statorcore with a difference in level provided between the plurality of statorcores.

This provides a stator core able to easily unfold and divide wiring.

The method of manufacturing a rotary core according to the presentinvention includes a stator connected both ends of the stator core bybending a stator core in a ring having a plurality of stator cores, eachmade up of a prescribed number of stacked sheet magnetic materials; aplurality of yoke members forming each the stator core; a bendable bentportion provided between the yoke members; and an interconnectingportion for interconnecting the plurality of stator cores by connectingthe upper end of one stator core to the lower end of the other statorcore with a difference in level provided between the plurality of statorcores; and a base member equipped with the stator core.

This provides a rotary motor superior in the mass productivity.

The disk drive unit according to the present invention includes a statorcore divided from a stacked stator core provided with a plurality ofstator cores, each stator core makde up of a prescribed number ofstacked sheet magnetic materials; a plurality of yoke members formingeach stator core; a bendable bent portion provided between the yokemembers; an interconnecting portion for interconnecting the plurality ofstator cores by connecting the top of one stator core to the bottom ofthe other stator core with a difference in level provided between theplurality of stator cores; and a portion for reading and writing datafrom and to magnetic recording media rotated by the rotary motor.

This provides a slim and low-cost disk drive unit.

The method of manufacturing a rotary motor according to the presentinvention includes the steps of stacking a prescribed number ofring-shaped sheet magnetic materials provided with a plurality of yokemembers and having a first divided portion at one place between the yokemembers and a bent portion at the other place therebetween, such thateach first divided portion is placed at the same position; stacking aprescribed number of sheet magnetic materials such that second dividedportions thereof are placed with a prescribed number shifted by a unitof yoke members in the circumferential direction relative to theprescribed number of stacked sheet magnetic materials; successivelystacking the sheet magnetic materials to form a stacked stator core byrepeating the two steps as many as a desired number of times; elongatingthe bent portions of the stacked stator core to unfold the stackedstator core straight; winding driving coils around the magnetic poleteeth provided on the yoke members; dividing the wound yoke members intostator blocks; and forming a ring-shaped stator by bending the dividedstator at the bending portion and connecting both ends thereof.

This provides the workability in the winding process and the massproductivity of a stator and rotary motor.

The method of manufacturing a rotary motor according to the presentinvention includes stacking a prescribed number of ring-shaped sheetmagnetic materials provided with a plurality of yoke members and havinga bent portion between the yoke members and a first divided portion inthe vicinity of one the bent portion, such that each first dividedportion is placed at the same position; stacking a prescribed number ofsheet magnetic materials having a second divided portion at the positionopposed to the first divided portion through the bent portion on thestacked sheet magnetic materials, such that each second divided portionis placed at the same position; stacking a prescribed number of sheetmagnetic materials such that third divided portions thereof arepositioned with a prescribed number shifted by a unit of yoke members inthe circumferential direction relative to the prescribed number ofstacked sheet magnetic materials having the second divided portion;successively stacking the sheet magnetic materials to form a stackedstator core by repeating the three steps as many as a desired number oftimes. elongating the bent portions of the stacked stator core to unfoldthe stacked stator straight; winding driving coils around the magneticpole teeth provided on the yoke members; dividing the wound yoke membersinto stator blocks; and forming a ring-shaped stator by bending thedivided stator at the bending portion and connecting both ends thereof.

This improves the workability in the winding process and the massproductivity of a rotary motor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the partially unfolded structure ofthe stacked stator core according to a first embodiment of the presentinvention;

FIG. 2 is a front view showing the partially unfolded structure of thestacked stator core shown in FIG. 1;

FIG. 3 is a sectional view showing the section taken along line III—IIIin FIG. 2;

FIG. 4 is a sectional view showing the section taken along line IV—IV inFIG. 2;

FIG. 5 is a perspective view showing a step of manufacturing the statorby the stacked stator shown in FIG. 1;

FIG. 6 is a perspective view showing the second step of manufacturingthe stator shown in FIG. 5 different from FIG. 5;

FIG. 7 is a perspective view showing the third step of manufacturing thestator shown in FIG. 5;

FIG. 8 is a perspective view showing the fourth step of manufacturingthe stator shown in FIG. 5;

FIG. 9 is a plan view showing the structure of the stator manufacturedby going through each step;

FIG. 10 is a perspective view of the rotary motor;

FIG. 11 is a perspective view of the stator used for the rotary motor;

FIG. 12 is a partially enlarged view of the unfolded stator;

FIG. 13 is a partially enlarged view of the unfolded stator core;

FIG. 14 is an exploded perspective view of the rotary motor;

FIG. 15 is a perspective view of the stacked stator core used for thestator core of the rotary motor;

FIG. 16 is a partially unfolded perspective view of the stacked statorcore;

FIG. 17 is a schematic view of the elongated stacked stator core;

FIG. 18 is a perspective view showing the state in which the magneticmaterials of the stacked stator core are stacked;

FIG. 19 is a schematic view showing the application of insulationcoating to the stacked stator core;

FIG. 20 is a partially enlarged view of the stacked stator core;

FIG. 21 is a perspective view showing the steps in which the statorcores are divided from the stacked stator core and the driving coils arewound around the stator core;

FIG. 22 is a perspective view showing the steps in which the drivingcoils are wound around the divided stator core and formed in a ring;

FIG. 23 is a partially enlarged view in the vicinity of the bent portionof the stator core and a sectional view thereof;

FIG. 24 is a plan view showing the angle pitches of the magnetic poleteeth;

FIG. 25 is a view showing the method of manufacturing stators after thedriving coils are wound;

FIG. 26 is a view showing the state in which the rotor of the rotarymotor is provided with the cover table according to a second embodiment;

FIG. 27 is a view showing the sectional structure in which the number ofcoil winding of the driving coil wound around the magnetic pole teeth ofthe stepped yoke member is smaller than that of the yoke member;

FIG. 28 is a view showing the sectional structure in which the stator ismounted on the base with a gradient such that the step yoke member sideis lower than the level shown in FIG. 26 and the height Hh of the topsurface of the driving coil wound around the magnetic pole teeth of thestep yoke member is the same as the height Hf of the top surface of thedriving coil wound around the magnetic pole teeth of the yoke member;

FIG. 29 is a view showing the method of eliminating the difference inlevel of the step yoke member by press-forming the step yoke member;

FIG. 30 is a view showing the method of eliminating the difference inlevel of the step yoke member by press-forming the step yoke member;

FIG. 31 is a view showing the method of eliminating the difference inlevel of the step yoke member by press-forming the step yoke member;

FIG. 32 is a perspective view of the rotary motor;

FIG. 33 is a perspective view of the stator for the rotary motor;

FIG. 34 is a partially enlarged view of the unfolded stator;

FIG. 35 is a partially enlarged view of the unfolded stator core;

FIG. 36 is a perspective view showing the state in which the stackedstator core is partially unfolded;

FIG. 37 is a schematic view of the elongated stacked stator core;

FIG. 38 is a perspective view showing how the magnetic materials of thestacked stator core are stacked;

FIG. 39 is a perspective view showing the steps in which the drivingcoils are wound around the stator core divided from the stacked statorcore and the stator sore is formed in a ring;

FIG. 40 is a perspective view showing the step in which the stator ismounted on the base;

FIG. 41 is a perspective view showing the state in which the stackedstator core is partially unfolded;

FIG. 42 is a schematic view of the elongated stacked stator core;

FIG. 43 is a perspective view showing the steps in which the drivingcoils are wound around the stator core divided from the stacked statorcores;

FIG. 44 is a plan view showing the state in which the stator core isformed in a ring;

FIG. 45 is a partial plan view showing the state in which the yokemembers are unfolded at the bent portion;

FIG. 46 is a sectional view of the bent portion;

FIG. 47 is an external view of the floppy disk drive unit equipped withthe rotary motor manufactured based on the stacked stator core accordingto the above embodiments;

FIG. 48 is a view showing a part of steps in a conventional method ofmanufacturing stators; and

FIG. 49 is a view showing a part of steps in a conventional method ofmanufacturing stators.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

The first embodiment of the present invention will next be describedwith reference to the drawings. FIG. 1 is a partially unfoldedperspective view showing the structure of the stacked stator core in thefirst embodiment of the present invention. FIG. 2 is a front viewshowing the structure of the stacked stator core shown in FIG. 1. FIG. 3is a sectional view showing the section taken along line III—III in FIG.2. FIG. 4 is a sectional view showing the section taken along line IV—IVin FIG. 2. FIG. 5 is a perspective view showing a step of manufacturingthe stator by the stacked stator shown in FIG. 1. FIG. 6 is aperspective view showing the second step of manufacturing the statordifferent from FIG. 5. FIG. 7 is a perspective view showing the thirdstep of manufacturing the stator shown in FIG. 5. FIG. 8 is aperspective view showing the fourth step of manufacturing the statorshown in FIG. 5. FIG. 9 is a plan view showing the structure of thestator manufactured by going through each step.

Referring to the FIGS. 1 to 8, reference numeral 10 denotes a first coremember 10 formed by stacking, for instance, five magnetic materials andmade up of three yoke members 1,2 and 3 connected to one another througha thinned portion m as a bendable bent portion. The yoke members 1 and 3have on one side a plurality of projecting pole teeth 1 a and 3 a, andthe yoke member 2 has on one side a plurality of projecting edges 2 afor twinning the terminal of a winding to be described later.

Reference numeral 20 denotes a second core member formed by stackingfive magnetic materials similar to the first core member 10 and made upof yoke members 4 arranged in such a manner that one end of eachmagnetic material of the second core member 20 is successively connectedto the second stage of the other end of the first core member 10 througha thinned portion m from the second magnetic material of the other endof the first core member 10 by shifting entirely the second core member20 downwards, with left one stage of one end of the second core member20 unconnected. The yoke member 4 has on one side a plurality ofprojecting edges 4 a similar to the projecting edges 2 a on the yokemember 2.

Reference numeral 30 denotes a third core member formed by stacking fivemagnetic materials similar to the first and second core members 10 and20, each of which is made up of three yoke members 5, 6 and 7 as many asthe first core member 10 connected through a thinned portion m. One endof the first magnetic material of the third core member 30 is connectedto the other end of the last magnetic material of the second core member20 through a thinned portion m by shifting entirely the third coremember 30 downwards. The yoke members 5 and 7 have on one side aplurality of projecting magnetic teeth 5 a and 7 a, and the yoke member6 has on one side a plurality of projecting edges 6 a similar to eachprojecting edge 2 a and 4 a.

Reference numeral 40 denotes formed by stacking five magnetic materialssimilar to the third core member 30 and made up of a yoke member 8arranged in such a manner that one end of each magnetic material of thefourth core member 40 is successively connected to the second stage ofthe other end of the third core member 30 through a thinned portion mfrom the second magnetic material of the other end of the third coremember 30 by shifting entirely the fourth core member 40 downwards, withleft one stage of one end of the fourth core member 40 unconnected. Theyoke member 40 has on one side projecting edges 8 a similar to eachprojecting edge 2 a, 4 a and 6 a. The first, second, third and fourthcore members are independently arranged in a ring and mutually stacked.

The method of manufacturing the stacked stator core 50 formed asmentioned above and a stator using this stator core will now bedescribed.

First of all, four sheets of magnetic material are formed bysuccessively forming them into the shape shown in FIG. 3 by blankingusing a successive die, and drilled to form small holes in the vicinityof the outer contour of corners C1, C2 and C3 of the corners C1, C2, C3and C4. Then, slits are formed by cutting and bending the materialbetween the small holes and the inner contour to form a bendable thinnedportion m between the small holes and the outer contour in each corner.Also, in corner C4, a slit is formed between the outer and innercontours by cutting and bending the material to from the slit runningfrom the inner contour to the outer contour.

Secondly, in the same manner as the above, one sheet of magneticmaterial is formed into the shape shown in FIG. 4, by further stackingit on the magnetic material as mentioned above, and drilled to formsmall holes in the vicinity of the outer contour of corners C1, C2 andC4 out of the corners C1, C2, C3 and C4. Then, slits are formed bycutting and bending the material between the small holes and the innercontour to form a bendable thinned portion m between the small holes andthe outer contour in each corner. Also, in corner C3, a slit is formedbetween the outer and inner contours by cutting and bending the materialto form the slit running from the inner contour to the outer contour.Then, the stacked magnetic material is caulked at the places marked witha circle in FIGS. 3 and 4 to fix and integrate the magnetic materialinto the yoke members 5, 6, 7 and 8.

Subsequently, in the same manner as the above, four sheets of magneticmaterial are formed into the shape shown in FIG. 3, stacked, and drilledto form small holes in the vicinity of the outer contour of corners C1,C2 and C3, out of the corners C1, C2, C3 and C4. Then, slits are formedby cutting and bending the material between the small holes and theinner contour to form a bendable thinned portion m between the smallholes and the outer contour in each corner. Also, in corner C4, a slitis formed between the outer and inner contours by cutting and bendingthe material, to form the slit running from the inner contour to theouter contour.

After that, in the same manner as the above, one sheet of magneticmaterial having the shape shown in FIG. 4 is formed, further stacked onthe stacked magnetic material as mentioned above, and drilled to makesmall holes in the vicinity of the outer contour of corners C1, C2 andC4 out of the corners C1, C2, C3 and C4. Then, slits are formed bycutting and bending the material between the small holes and the innercontour to form bendable thinned portion m between the small holes andthe outer contour in each corner. Also, in corner C3, a slit is formedbetween the outer and inner contours by cutting and bending the materialto form the slit running from the inner contour to the outer contour.Then, the stacked magnetic material is caulked at the places marked witha circle in FIGS. 3 and 4 to fix and integrate the magnetic materialinto each of yoke members 1, 2, 3 and 4.

As mentioned above, a ring made up of yoke members 5 to 8 and anotherring made up of yoke members 1 to 4 are stacked in the state in whichthe lowest magnetic material of yoke member 4 and the highest magneticmaterial of yoke member 5 are connected through thinned portion m tofinish a stator core 50. In the state in which a prescribed number ofthe stacked stator cores 50 are stacked by a predetermined number ofstages, the stacked stator cores are taken out of a mold as a block.

Stacked stator cores 50 thus taken out of the mold in the stacked stateare transferred to the next process by a pallet 11 as shown in FIG. 5.Then, the stacked stator cores 50 are placed on a tension roller 12, andthe core members are successively withdrawn from the uppermost stackedstator cores in the direction indicated by an arrow as shown in FIG. 6to unfold the stacked stator cores. In the next process, as shown inFIG. 7, the unfolded stacked stator cores are hung by a hanger 13, anddipped in a coating bath 14 to apply electrocoating. Then, the stackedstator core 50 terminated in the electrocoating process in the unfoldedstate are transferred to the next winding process.

In the winding process, as shown in FIG. 8, a magnet wire 17 drawn outfrom a receiving drum 16 is wound around the pole teeth 1 a, 3 a, 5 aand 7 a by a winding machine 15 in the order of yoke members 1, 3, 5 and7, and the terminal of the wire is twined around the projecting edges 2a, 4 a, 6 a and 8 a of the yoke members 2, 4, 6, and 8, respectively.Subsequently, the yoke members 1 to 4 are wound up by a winding machine18 in a ring, and as shown in FIG. 9, by cutting the thinned portion m,through which the magnetic material of the lowest yoke member 4 and themagnetic material of the highest yoke member 5 are connected. A stator60 is finished, in which a winding 19 is wound around the projectingedges 1 a and 3 a of the yoke members 1 and 3 respectively, and aterminal 19 a is twined around the projecting edges 2 a and 4 a of yokemembers 2 and 4 respectively.

Similarly, stators 60 are finished successively by cutting the thinnedportion m connected in the yoke members 5 to 8 and the yoke members 1 to4 sequence, and successively winding up the yoke members in a ring.

As mentioned above, according to the first embodiment, the stackedstator core 50 is formed by blanking, and cutting and bending processesshown in FIGS. 3 and 4 repeated for every prescribed number of magneticmaterials using a progressive die. Then, a plurality of these stackedstator cores are stacked to form a block, and thus formed block of thestacked stator core 50 is withdrawn straight from the block forunfolding. After electrocoating and winding in the unfolded state, thestacked stator core is successively wound up in a ring again toconsecutively form stators 60. This facilitates the unfolding ofwinding, and improves the workability in winding process. At the sametime, it provides a stacked stator core capable of increasing massproduction and the method of manufacturing thereof.

Naturally, without restricted to the above. Since the bent portionintervening in the yoke members 1 to 8 is formed by a thinned portion mmade up of a small hole and a slit, the process therefore becomes easy.Additionally, since the number of the magnetic material connecting thesecond and the third core members 20 and 30, and the fourth and thefirst core members 40 and 10 is limited to only one, the cutting processbecomes easy when winding up the core as a core in a ring again afterthe winding process is done. Moreover, since the magnetic materials areblanked and caulked at the same time for every yoke members 1 to 8 whenblanking the magnetic materials, the post process can be omitted afterintegration. This make it possible to improve the workability in theassembly process and mass productivity.

In addition, in the above structure of the stator 60, no winding iswound around the yoke members 2, 4, 6 and 8, and the yoke membersfunction as a so-called magnetic balancer. Even if there is no space forwinding the yoke members 2, 4, 6 and 8 by the reason of arrangement ofperipheral devices, the stator can be used. Moreover, in the abovestructure of the stator 60, when the stacked stator core is wound up ina ring after winding, the core is wound such that the side on which thewinding 19 is wound faces the inside of the core to implement aninner-rotor type stator 60. Alternatively, the shape of the stackedstator core may be slightly changed for the wound side to face theoutside of the core to form an outer-rotor type stator 60.

In the first embodiment, the description is given, assuming that onestator 60 is made up of the first core member 10 and second core member20. However, it is also possible to consider that as a whole, one stator60 is formed by one core made up of a prescribed number of stacked sheetmagnetic materials, i.e., one stator core used for one rotary motor. Inother words, as is apparent from FIG. 2, first of all, four sheetmagnetic materials are stacked such that they are completely overlapped;then new one sheet magnetic material is stacked over the four stackedsheet magnetic materials with the new one sheet magnetic materialshifted relative to the above four stacked sheet magnetic materials; andsubsequently one yoke member of the new four stacked sheet magneticmaterials are overlapped over the above overhung part of the one sheetmagnetic material. This forms a stacked stator core 50 made up ofsuccessively stacked stator cores while holding a prescribed number ofstacked layers as a whole.

Second Embodiment

Second embodiment of the present invention will now be described withreference to FIGS. 10 to 14. FIG. 10 is a perspective view of the rotarymotor. FIG. 11 is a perspective view of the stator used for the rotarymotor. FIG. 12 is a partially enlarged view of the unfolded stator. FIG.13 is a partially enlarged view of the unfolded stator core. FIG. 14 isan exploded perspective view of the rotary motor. In FIGS. 10 to 14,reference numeral 71 denotes a base, reference numeral 72 a rotor, andreference numeral 73 a stator.

As shown in FIG. 14, the base 71 is provided with stator fastening pins101 having a support flange 101 a and an engaged portion 101 b toposition and fasten the stator 73, a stator supporting pin 102 toposition the stator 73, coil terminal lands 103,104 and base fasteningholes 105 for fastening the base 71. A rotor 72 is provided with a shaft201 engaged and supported by the base 71 in the center of the base 71.The base 71 is pivotally provided with a turntable 202 engaged and fixedby the shaft 201 and a ring-shaped rotor magnet 203 fixed to theperiphery of the turntable 202 and magnetized such that the periphery ofthe rotor magnet 203 has multipole.

As shown in FIGS. 11 to 13, a stator 73 is made up of a stator core 300formed by stacking sheet magnetic materials and driving coils 350 whosemagnetic pole teeth 302 are wound by a wire. In addition, the statorcore 300 is provided with yoke members 301 made up of magnetic poleteeth 302 of the number provided in proportion to the number of drivingphase and yokes 303 having tooth-shaped magnetic pole teeth 302, astepped yoke member 309 provided with magnetic pole teeth 302 and yoke303 similar to other yoke members 301 and having a sheet magneticmaterial partially not connected with other yoke members 301, bentportions 304 connecting the yoke members, stator positioning protrusions305 arranged opposed to each other on both sides of the bent portion 304in the same direction as that of magnetic pole teeth 302, caulkings 306,307 to fix and integrate the stacked sheet magnetic materials, and coreconnecting portions 308 provided at the ends of the stator core 300, anda driving coil 350 wound around each magnetic pole teeth 302.

Stator positioning protrusions 305 are provided for forming a hole withwhich stator fastening pins 101 are engaged when the stator 73 isarranged in a ring as shown in FIGS. 10 and 11. In other words, when thestator 73 is arranged in a ring, one stator positioning protrusion 305(a first positioning hole) provided at the end of one yoke member 301and the other stator positioning protrusion 305 (a second positioninghole) provided at the end of the other yoke member 301 adjacent to theone yoke member 301 are bent at the bent portion 304 as a fulcrum, andthereby two stator positioning protrusions 305 move to the position inwhich the protrusions oppose each other to form a hole to engage withthe stator fastening pin 101.

Similarly, core connecting portions 308 are provided to engage thering-shaped stator 73 with the stator supporting pin 102 in such amanner that a hole is formed with the core connecting portions 308 atboth ends of the core opposing each other. Therefore, the engagement ofthe positioning holes and the stator fastening pins 101 easily fixes thestator 73 on the base 71.

Here, as shown in the sectional view of FIG. 2 in the first embodiment,the stepped yoke members, i.e., the fourth yoke members 4, 8 in FIG. 2are formed by stacking the same number (five) of sheet magneticmaterials as that of the other yoke members, i.e., the first to thirdyoke members 1 to 3, 5 to 7 in FIG. 2. For this reason, the stepped yokemembers are shifted from the other yoke members by one sheet magneticmaterial in the stacking direction, and a difference in level(projection) is provided relative to the other yoke members.

Coil terminals 351 at one end side of each phase of the driving coils350 shown in FIG. 10 are led through the lower part of the stepped yokemember 309 and soldered to the coil terminal land 103. Coil terminals atthe other end of each phase are twisted, combined and soldered to thecoil terminal land 104 as a common coil terminal 352.

In order to arrange the stator 73 in a ring as shown in FIGS. 10 and 11or straight as shown in FIG. 12, the bent portions 304 are provided ateach connecting part between the yoke members so as to make the yokemembers 301 or the stepped yoke member 309 bendable. Additionally, eachmagnetic pole teeth 302 of the yoke members 301 and stepped yoke member309 are provided so as to make the magnetic pole teeth 302 parallel toeach other within each of the yoke members.

A rotary motor 80 so arranged as above can rotate the rotor 72 byfeeding a prescribed amount of current to each driving coil 350.Moreover, the provision of the stepped yoke member 309 exerts the momentof a force in the rotor 72 in which the rotation axis 201 inclinestoward the stator 73 because the forces of attraction acting on therotor 72 are different between the yoke members 301 and stepped yokemembers 309 in the direction of the rotation axis 201 of the rotor 72.As a result, it is possible to stabilize the rotation of the rotor 72even when an oscillation or the like is applied to the rotary motor 80.

In addition, the coil terminals 351 are led through the lower part ofthe stepped yoke member 309 and soldered to the coil terminal lands 103.As a result, the coil terminal 351 can be led through a more largerspace than the lower part of the other yoke members 301, improvingproductivity in wiring.

The method of manufacturing the above rotary motor 80 will now bedescribed.

First of all, the stator core 300 for the rotary motor 80 will bedescribed with reference to FIGS. 15 to 18. FIG. 15 is a perspectiveview of the stacked stator core for the stator core 300 of the rotarymotor 80. FIG. 16 is a perspective view of the partially explodedstacked stator core. FIG. 17 is a schematic view of stator cores withextremely elongated between the stator core at connection parts. FIG. 18is a perspective view showing the state how the sheet magnetic materialsof the stacked stator core are stacked.

Referring to FIG. 15, reference numeral 50 denotes a stacked stator coreformed by stacking a plurality of stator cores 300 in a ring and eachstator core 300 is successively connected through stator core connectingportions (interconnection portions) 401. Further, as shown in FIG. 16,the stator cores 300 can be successively unfolded straight by bendingthe bent portions 304. As shown in FIGS. 16 and 17, a stator core madeup of portion 401 consists of a bent portion 304 provided between astepped yoke member 309 and the stator core 300 adjacent to the steppedyoke member 309, in the state of stacked stator core 50. As shown inFIG. 18, such stacked stator core 50 can be manufactured by mutuallyoverlapping the same magnetic materials where a first divided portion411 thereof is provided at the same place, i.e., stacked core 412 madeup of four magnetic material cores 410 stacked such that the firstdivided portions 411 thereof are placed at the same position and amagnetic material core 420 having the same shape as that of magneticmaterial core 410 and a second divided portion 421 at the positionshifted by 60°. The angle of 60° is calculated based on the fact thatsince in the second embodiment, six yoke members (five yoke members 301and one stepped yoke member) in total have been provided, the angle madewith one yoke member is 60° (360°÷6=60°). Here, in the abovedescription, the case is shown in which the shift is done in an amountof one yoke member 301. Alternatively, if a stacked stator core 50 isformed by shifting the magnetic material core in the amount of aplurality of yoke members, for instance, two yoke members 301 (that is,by 120° in the second embodiment), the same effect may also be obtained.

In FIG. 18, the core connecting portion 401 corresponds to the bentportion 304 in the magnetic material core 420. When the part 309 aadjacent to the second divided portion 421 in the magnetic material core420 is stacked, stepped yoke member 309 is formed. When cut at thestator core connecting portion 401, each magnetic material core 410 and420 is connected with caulkings 306 and 307 as shown in FIG. 13.

Application of insulation coating to the stacked stator core 50 willnext be described with reference to FIGS. 19 and 20. FIG. 19 is aschematic view showing the application of insulation coating to thestacked stator core 50. FIG. 20 is a partially enlarged view of thestacked stator core 50.

Referring to FIG. 19, reference numeral 74 denotes an electrocoatingbath, and coating liquid 75 is being filled therein. An elongatedstacked stator core 50 is dipped in the coating liquid 75. Applicationof a voltage between an electrode (not shown) placed in the coatingliquid 75 and the stacked stator core 50 forms insulation coating film430 over the stacked stator core 50. In order to enable the stackedstator core 50 to unfold by the bending bent portion 304 as shown inFIG. 16, a gap in opening 305 a between the ends of stator positioningprotrusions 305 opposing each other before coating have been previouslyset such that the relationship of a>2 b is kept with respect to thethickness b of the insulation coating film 430, not to close the opening305 a by the insulation coating. Insulation coating using cationicelectrocoating, for instance, is popular as the insulation coatingmethod.

Wiring of the driving coils 350 wound around the stacked stator core 50and mounting of the wire-wound stator 73 on the base 71 will bedescribed with reference to FIG. 14, FIGS. 21 and 22. FIG. 21 is aperspective view showing the steps in which the stator cores 300 aredivided from the stacked stator core 50 and the driving coils 350 arewound around the divided stator core 300. FIG. 22 is a perspective viewshowing the steps in which the driving coils 350 are wound around thedivided stator core 300 and unfolded a stator 73 is formed in a ring.FIG. 14 is an exploded perspective view of the step in which the stator73 is mounted on the base 71.

As shown in FIGS. 21 and 22, the stator cores 300 are unfolded from thestacked stator core 50 and divided at the stator core connecting portion401 (FIG. 16). FIG. 22A is a view of a divided stator core 300. Then,the driving coils 350 are simultaneously wound around the magnetic poleteeth 302 of the yoke members 301 by a winding machine 360 (FIG. 22B).The wire-wound stator 73 is bent at the bent portions 304 and arrangedin a ring (FIG. 22C). As shown in FIG. 14, the ring-shaped stator 73 ismounted on the base 71. A rotary motor 80 is finished by soldering coilterminals 351 and a common coil terminal 352 with coil terminal lands103 and a coil terminal land 104, respectively.

Adoption of such a method of manufacturing stators used for rotarymotors improves both the workability in the winding process, and themass productivity of the stators and rotary motors.

The shape of the stator core 300 of the above rotary motor 80 will bedescribed with reference to FIGS. 23 and 24. FIG. 23 is a partiallyenlarged view and a corresponding sectional view in the vicinity of thebent portion 304 of the stator core 300. FIG. 24 is a plan view showingthe angle pitches of the magnetic pole teeth 302. The width c of bentportion 304 in the diameter direction is set such that the width csatisfies the relationship of 1.5t≦c≦2.5t for the thickness t of onestacked sheet magnetic material. The reason why this relationship isestablished is to prevent the bent portion 304 from being divided whenthe stator core 300 is unfolded straight by bending the bent portion 304to wind the driving coil 350, and subsequently the stator 73 is arrangedin a ring by again bending the bent portion 304 of the stator core 300.An experimental investigation of the relationship between the width cand the thickness t of the bent portion 304 in terms of the bendingtimes of the bent portion 304 revealed that the the bent portion 304 canendure several times of bending if the width c of the bent portion 304is 1.5t or more. However, it turned out that inasmuch as the width c ofbent portion 304 is set up too large, the bending at the prescribedposition of the bent portion 304 is sometimes failed and so can not takethe arrangement in a ring when one tries to make the stator 73 in aring. It is experimentally proved that the suitable width c of bentportion 304 is 2.5t or less.

Moreover, as shown in FIG. 24, it is possible to reduce the coggingtorque by setting the electrical angle pitches θb between magnetic poleteeth 302 located within one yoke member 301 and the electrical anglepitch θ between the magnetic pole tooth 302 located within the one yokemember 301 and a magnetic pole tooth 302 within the yoke member 301adjacent to the one yoke member 301 so as for the electrical anglepitches θb and θ to satisfy the relationship of θ≠θb. However, becausethe driving power of the rotary motor is lowered when the relationshipbetween θb and θ is significantly altered each other, it is preferablethat the suitable shift amount between both the electrical angle pitchesis 10° or less in electric angle. That is, the electric angle θsatisfying the relationship of θb−10°≦θ≦θb+10° and θ≠θb is advisable.

In the second embodiment, the stator core 300 is divided from thestacked stator core 50 and the driving coils 350 are wound around thestator core 300. Naturally, as shown in FIG. 25, if the stator 73 ismanufactured by dividing the stator core 300 from the stacked statorcore 50 after the driving coils 350 are wound around the stator core300, the same effect can be obtained. That is, it is needless to saythat the workability in the winding process, and the productivity of thestators and rotary motors can be improved.

Third Embodiment

In above second embodiment, a stator 73 is mounted on a rotary motor 80with a difference in level of one sheet magnetic material (magneticmaterial cores 410, 420) provided between the stepped yoke member 309and the yoke members 301.

A method of reducing the influence of the difference in level betweenthese yoke members caused by the stepped yoke member 309 will bedescribed. Like or equivalent members as that of the second embodimentare given like reference numerals, and thus the description thereof isomitted for brevity's sake.

FIG. 26 is a sectional view showing the state in which a cover table 210is provided over the rotor 72 of the rotary motor 80 in the secondembodiment to keep the invasion of dust or the like out of the cavitybetween the rotor magnet 203 and the stator 73. In FIG. 26, referencenumeral 110 denotes a bearing that engages with a shaft 201 installed inthe base 71. In this case, a difference in level is provided between theheight Ha of yoke member 301 and the height Hd of stepped yoke member309. When the cover table 210 is provided over the upper surface of thedriving coil 350 wound around the magnetic pole teeth 302 of the yokemember 301 through a prescribed space e, the cover table 210 comes intocontact with the driving coil 350 wound around the magnetic pole teeth302 of the stepped yoke member 309. As a result, the prescribedoperation of the rotary motor 80 is not accomplished, or the rotarymotor 80 does not rotate. One of the solutions to this problem is toincrease the space e. However, such a solution gives rise todifficulties in thinning the rotary motor 80 because the thickness ofthe motor itself increases.

In the third embodiment, a method of removing the influence of thestepped yoke member 309 while avoiding the trouble of increasingthickness of rotary motor 80.

One of effective methods is to reduce the number of winding of thedriving coil 350 wound around the magnetic pole teeth 302 of the steppedyoke member 309 compared with the number of winding of the driving coil350 wound around the magnetic pole teeth 302 of the yoke member 301 asshown in FIG. 27.

Another method is to mount the stator 73 onto the base 71 with agradient as shown in FIG. 28 such that the height of the driving coil ofthe stepped yoke member 309 is lower than the height thereof shown inFIG. 26. Then, the stator 73 is arranged such that the height Hf of theuppermost part of the driving coil 350 wound around the magnetic poleteeth 302 of yoke member 301 is identical with the height Hh of theuppermost part of driving coil 350 wound around the magnetic pole teeth302 of the stepped yoke member 309.

In addition, still another method is to press forming the stator core300 having the stepped yoke member 309 (FIG. 29A) as shown in FIG. 29such that the height of the stepped yoke member 309 becomes flush withthat of the other yoke members 301 (FIG. 29B) to eliminate thedifference in level of the stepped yoke member 309. After that, thedriving coils 350 are formed by winding a wire around each of magneticpole teeth 302 and a stator 73 is formed by bending each yoke member 301in a ring as shown in FIG. 30. Subsequently, the stator 73 are mountedand fixed onto the base 71 as shown in FIG. 31. This method of makingthe height of the stepped yoke member 309 flush with that of the yokemember 301 is extremely effective.

As mentioned above, thin rotary motors 80 can be easily implemented whenthe influence of the stepped yoke member 309 is removed by the abovemethods of changing the number of winding of the driving coil 350,mounting the stator 73 to the base 71 by inclining the stator 73, andpress forming the stepped yoke member 309.

Fourth Embodiment

As a structure in which yoke members are overlapped one another in thestator core, the stacked stator and rotary motor of the fourthembodiment 4 which increases mounting of the stator 73 on the base 71will next be described with reference to FIGS. 32 to 40. FIG. 32 is aperspective view of the rotary motor. FIG. 33 is a perspective view ofthe stator for the rotary motor. FIG. 34 is a partially enlarged view ofthe unfolded stator. FIG. 35 is a partially enlarged view showing thestate in which the stator core is unfolded. FIG. 36 is a perspectiveview showing the state in which the stacked stator core is partiallyunfolded. FIG. 37 is a schematic view showing the state in which thestacked stator core is elongated. FIG. 38 is a perspective view showingthe state in which the sheet magnetic materials of the stacked statorcore are stacked. FIG. 39 is a perspective view showing the steps inwhich the stator core 300 is divided from the stacked stator core 50,the driving coils 350 are wound around the stacked stator core 50, andsubsequently arranged in a ring. FIG. 40 is a perspective view showingthe step in which the stator 73 is mounted on the base 71. Like orequivalent members as that of the second embodiment are given likereference numerals and thus the description thereof is omitted forbrevity's sake.

As shown in FIG. 40, the base 71 is provided with stator fastening pins101 having a support flange 101 a and an engaging portion 101 b forpositioning and fastening the stator 73, a stator supporting pin 102 forpositioning the stator 73, and a rotor 72 pivotally connected thereto.

As shown in FIGS. 32 to 34, and FIG. 40, a stator 73 is made up of astator core 300 formed by stacking sheet magnetic materials, and drivingcoils 350.

The stator core 300 is provided with yoke members 301 made up ofmagnetic pole teeth 302 that is provided in proportion to the number ofdriving phase and yokes 303 having tooth-shaped magnetic pole teeth 302,bent portions 304 for connecting the yoke members 301, statorpositioning protrusions 305 arranged opposed to each other on both sidesof the bent portion 304 in the same direction as that of the magneticpole teeth 302, core connecting portions 321, 322 having punched thereonconnecting and fixing holes 323, 324, provided at the ends of the statorcore 300 such that the core connecting portions 321, 322 are overlappedone another when the stator core 300 is arranged in a ring, and astepped yoke member 309 is provided with the magnetic pole teeth 302 andyokes 303 as in other yoke members 301 and having partially a sheetmagnetic material not connected with other yoke members 301, with eachof the driving coils are being wound around the magnetic pole teeth 302.

Stator positioning protrusions 305 are provided so that holes engagingwith stator fastening pin 101 are formed in the state in which thestator 73 is arranged in a ring. Moreover, as shown in FIG. 32, FIGS. 33and 40, the core connecting portions 321 and 322 are also provided suchthat the core connecting portions 321, 322 located at both ends areoverlapped one another and the connecting and fixing holes 323 and 324engage with the stator supporting pin 102 when the stator 73 is arrangedin a ring.

The stepped yoke member 309 and other yoke members 301 have the samenumber (five) of stacked sheet magnetic materials, and therefore adifference in level of a sheet magnetic material is provided because thestepped yoke member 309 is shifted by a sheet magnetic material fromother yoke members 301 toward the upper surface relative to the stackingdirection.

The rotary motor 80 so arranged as above can rotate rotor 72 by feedinga prescribed amount of current through each driving coil 350. Moreover,the provision of stepped yoke member 309 makes difference in the forcesof attraction acting on the rotor 72 between yoke members 301 andstepped yoke members 309 in the direction of the rotation axis 201 ofrotor 72. As a result, the moment of a force of the direction in whichthe rotation axis 201 inclines toward the stator 73 is exerted on rotor72, and it becomes possible to stabilize the rotation of rotor 72 evenwhen an oscillation or the like is applied to the rotary motor 80.

Moreover, the core connecting portions 321,322 having connecting andfixing holes 323, 324 are provided at both ends of the stator core 300so that the stator supporting pin 102 engages with the connecting andfixing hole 323, 324. Therefore, the workability and positioning areimproved when the stator 73 is arranged in a ring and fixed on the base71, and it becomes possible to firmly fix the stator 73 on the base 71.

The method of manufacturing such rotary motor 80 will now be described.

First of all, a stator core 300 used for the rotary motor 80 will bedescribed with reference to FIGS. 36 to 38. Referring to the FIGS. 36 to38, reference numeral 50 denotes a stacked stator core formed in such amanner that a plurality of stator cores 300 having a ring are stackedand each the stator core 300 is successively connected through statorcore connecting portions 401. As shown in FIG. 36, stator cores 300 canbe unfolded straight by bending bent portions 304.

As shown in FIG. 38, such stacked stator core 50 is manufactured bysuccessively overlapping the following parts: a stacked core A453 formedby overlapping two magnetic material cores 452 having a first dividedportion 451 provided in the vicinity of the part corresponding to thecore connecting portion 321, which are the same to each other and areoverlapped such that the first divided portions 451 thereof are placedat the same position; a stacked core B456 formed by overlapping twomagnetic material cores 455 that are in mirror image relation to themagnetic material core 452, i.e., correspond to the material core 452turned reversely at an angle of 180 degree, have a second dividedportion 454 provided in the vicinity of the part corresponding to thecore connecting portion 322, and overlapped one another; and a magneticmaterial core 458 having a partially notched stator core connectingportion 401 provided for omitting connecting and fixing holes 323, 324at the part corresponding to the position of bent portion 304 and athird divided portion 457 provided at bent portion 304 located in theposition away from the stator core connecting portion 401 by a distanceof one yoke member. In FIG. 18, reference numeral 301 a denotes the partto be yoke member 301 when stacked, and the numeral 309 a denotes thepart to be stepped yoke member 309 when stacked, respectively.

The stacked core A 453, the stacked core B 456, and the magneticmaterial core 458 are connected to each other by caulkings 306, 307 asshown in FIG. 35 when cut at stator core connecting part 401. Winding ofthe driving coils 350 wound around the stacked stator core 50 andmounting of the stator 73 on the base 71 are carried out in the samemanner as the second embodiment as shown in FIG. 36, FIGS. 39 and 40. Asshown in FIG. 36, stator cores 300 are unfolded from the stacked statorcore 50 and divided at the stator core connecting portion 401. Then, thedriving coils 350 are consecutively wound around the magnetic pole teeth302 of the yoke members 301 by a winding machine 360. The wire-woundstator 73 is bent at the bent portions 304 and arranged in a ring. Asshown in FIG. 40, the ring-shaped stator 73 is mounted on the base 71. Arotary motor 80 is finished by soldering coil terminals 351 and a commoncoil terminal 352 with coil terminal lands 103 and 104, respectively.The adoption of the above method of manufacturing rotary motors improvesworkability in the winding process and the productivity of rotarymotors. In addition to the above effects, when the stators 73 arearranged in a ring and fixed on the base 71, the workability andpositioning are improved, and it becomes possible to firmly fix thestators 73 on the bases 71.

Fifth Embodiment

In the above second and fourth embodiments, in order to manufacture astacked stator core 50, sheet magnetic materials are stacked for formingthe yoke members 301 (including the stepped yoke member 309) located onboth sides of the stator core connecting portion 401 connecting thestator cores 300, and joined by caulking 306, 307. For this reason, astepped yoke member 309 is formed after the stator cores are divided atthe stator core connecting portion 401. The fifth embodiment providesconnecting means for connecting stator cores 300 in which no differencein level is provided between the magnetic pole teeth 302 around whichthe driving coils 350 are wound.

The fifth embodiment will be described with reference to FIGS. 41 to 43.

FIG. 41 is a perspective view showing the state in which the stackedstator core 50 is partially unfolded. FIG. 42 is a schematic viewshowing the state in which the stator core is elongated. FIG. 43 is aperspective view showing the steps in which the stator core 300 isdivided from the stacked stator core 50 and the driving coils 350 arewound around the stator core 300. Like or equivalent members as that ofthe second and fourth embodiments are given like reference numerals andthus the description thereof is omitted for brevity's sake.

In FIGS. 41 and 42, reference numeral 401 denotes the stator coreconnecting portion. In the sheet magnetic materials provided on one endside of the stator core connecting portion 401 and placed on yokemembers 301, a connecting leaf 470 having the similar shape to that ofbent portion 304 is connected with a yoke member 301 by a caulking 471,and the opposing end (opposing the connecting leaf 470) is made up ofmagnetic pole teeth 302 and a yoke 303 forming the yoke member 301. Inother words, the connecting leaf 470 functions as an interconnectingportion. Such an arrangement as mentioned above brings about the stateshown in FIG. 43, when a stator core 300 is divided from the stackedstator core 50 at the stator core connecting portion 401. That is,although the connecting leaf 470 yet remains at the end of the statorcore 300, there is provided no difference in level between yoke members301 in the part of magnetic pole teeth 302 around which the drivingcoils 350 are wound. Therefore, a slim stator 73 having no difference inlevel can be provided, even through the stacked stator core 50 is used.

Sixth Embodiment

In the above second and fourth embodiments, the bent portion 304 isformed at the part having a thickness thinner than that of yoke 303 madeup of the yoke member 301. Alternatively, a bent portion that is moreeasily bent will next be described with reference to FIGS. 44 to 46.

FIG. 44 is a plan view showing the state in which the stator core 300 isarranged in a ring. FIG. 45 is a partial plan view showing the state inwhich the yoke member 301 is unfolded in the bent portion. FIG. 46 is asectional view of the bent portion. Like or equivalent members as thatof the second and fourth embodiments are given like reference numeralsand thus the description thereof is omitted for brevity's sake.

In FIGS. 44 to 46, reference numeral 340 denotes a bent portionconnecting yoke members 301. In the center of the bent portion 340positioning fastening holes 341 are provided for mounting and fixing astator 73 on a base 71. As shown in FIG. 46, one to four layers of sheetmagnetic materials are stacked such that recesses 342 and protrusions343 formed by half blanking the stacked sheet magnetic materials so asto engage each other. In the fifth layer of sheet magnetic material (theuppermost layer in FIG. 46) is provided a hole 344 engaging with theprotrusions 343 formed in the fourth layer of sheet magnetic material.In addition, in the sheet magnetic materials of each layer are providedgaps 345 having a prescribed width in the vicinity of bent portions 340so as for the bent portions 340 to be easily bent. A so-called jointstructure constructed by engagement of the recesses 342 and protrusions343 is arranged so as for yoke members 301 to be easily unfolded.

As mentioned above, letting the bent portion 340 to have a jointstructure makes it possible to eliminate the fracture of the bentportion 340 due to the fatigue of bent portion 340, thereby increasingthe reliability of the rotary motor 80, in the core structure like thestacked stator core 50 where it suffers from the frequent bending in thebent portion such as the unfold of stator core 300 or the restore to theoriginal arrangement of the stator 73 in a ring.

Seventh Embodiment

A floppy disk drive unit equipped with the rotary motor 80 manufacturedbased on the stacked stator core 50 according to the above embodimentswill now be described with reference to FIG. 47.

Referring to FIG. 47, reference numeral 601 denotes a loading unit,reference numeral 602 a magnetic head, reference numeral 603 a controlboard, reference numeral 604 a voice coil motor, and reference numeral605 a floppy disk, respectively.

A rotary motor 80 manufactured based on the stacked stator core 50 ismounted on the base of floppy disk drive unit nearly in the center ofthe disk drive unit. The magnetic record medium pivotally installedwithin the floppy disk 605 is rotated at a prescribed number ofrotations by means of the rotating torque of the rotary motor 80. Thereading and writing of data from and to such a floppy disk 605 is donevia the magnetic head 602. The voice coil motor 604 causes the magnetichead 602 to seek in the radius direction of floppy disk 605. The rotarymotor 80 and the voice coil motor 604 are accurately controlled by theelectric circuit provided on the control board 603.

The application of the rotary motor 80 according to the presentinvention to the floppy disk drive unit makes it possible to slim thefloppy disk drive unit and cut down the cost of the floppy disk driveunit.

The description of the above embodiment is made by way of the floppydisk drive unit. However, the similar effect may be obtained byapplication of the rotary motor 80 according to the present invention toother disk drive units having a drive mechanism actuated by a rotarymotor, hard disk drive units, CD-ROM drive units or the like, forinstance.

Industrial Applicability

As mentioned above, the stacked stator core according to the presentinvention provides stacked stator cores enabling easy transportation ofthe materials, easy mounting onto the winding machine, easy unfoldingand dividing of the stator cores for winding, and the assembly work.Further, it allows manufacture of rotary motors superior in massproductivity from the stacked stator core according to the presentinvention.

What is claimed is:
 1. A stacked stator core, comprising: a first coremember formed by stacking a prescribed number of magnetic materials andmade up of a plurality of yoke members connected to one another througha bendable bent portion; a second core member formed by stacking theprescribed number of magnetic materials and made up of a yoke memberarranged in such a manner that one end of each magnetic material of saidsecond core member is successively connected to the other end of saidfirst core member through a bendable bent portion from the next magneticmaterial of the other end of said first core member by shifting entirelysaid second core member downwards, with left the same number of stagesof one end of said second core member unconnected as the prescribednumber of stages; a third core member formed by stacking the prescribednumber of magnetic materials, each of which is made up of the samenumber of yoke members as said first core member connected through thebendable bent portion, and one end of the magnetic material of saidthird core member is connected to the other end of said second coremember through a bendable bent portion by shifting entirely said thirdcore member downwards; and a fourth core member formed by stacking theprescribed number of magnetic materials and made up of a yoke memberarranged in such a manner that one end of each magnetic material of saidfourth core member is successively connected to the next stage of theother end of said third core member through a bendable bent portion fromthe next magnetic material of the other end of said third core member byshifting entirely said fourth core member downwards, with left the samenumber of stages of one end of said fourth core member unconnected asthe prescribed number of sages; wherein the first, the second, the thirdand the fourth core members are independently arranged in a ring andmutually stacked.
 2. The stacked stator core according to claim 1,wherein the bent portion is formed by cutting and bending the magneticmaterial, leaving a thinned portion.
 3. The stacked stator coreaccording to claim 1, wherein said prescribed number of numbers is one.4. The stacked stator core according to claim 1, wherein the yoke memberis formed by caulking the stacked magnetic materials for integration ofthe magnetic materials.
 5. The stacked stator core according to claim 1,wherein said stator core is formed by stacking a plurality of magneticmaterials.
 6. A stacked stator core, comprising: a plurality of statorcores, each of which is made up of a prescribed number of stacked sheetmagnetic materials; a plurality of yoke members forming each statorcore; a bendable bent portion provided between said yoke members; and aninterconnecting portion for interconnecting said plurality of statorcores by connecting the upper end of one stator core to the lower end ofthe other stator core with a difference in level provided between saidplurality of stator cores.
 7. The stacked stator core according to claim6, wherein said interconnecting portion between said plurality of statorcores is formed by connecting the sheet magnetic material located at theuppermost position of one stator core to that at the lowermost positionof the other stator core so as to face each other.
 8. The stacked statorcore according to claim 6, wherein said interconnecting portion is madeup of one connecting member provided such that the uppermost end of onestator core is connected to the lowermost end of the other stator core.9. The stacked stator core according to claim 6, wherein said bentportion is formed by mutually caulking convexo-concave provided at bothends of each yoke member in each sheet magnetic material.
 10. A rotarymotor, comprising: a stator core having a plurality of yoke members,each yoke member making up of a prescribed number of stacked sheetmagnetic materials; a bendable bent portion provided between said yokemembers; a stepped yoke member whose one part of said yoke members isshifted from the other yoke members in the stacking direction of saidsheet magnetic materials relative to another yoke member; a statorformed by bending said stator core in a ring and connected both ends ofsaid stator core; and a base equipped with said stator.
 11. The rotarymotor according to claim 10, wherein the number of winding of thedriving coils wound around magnetic pole teeth provided on said steppedyoke member is smaller than that of another yoke members.
 12. The rotarymotor according to claim 10, wherein said stator is fitted with agradient relative to said base such that the top surface of the drivingcoils wound around magnetic pole teeth provided on said stepped yokemember are substantially flush with that of said another yoke members.13. The rotary motor according to claim 10, wherein said rotary motorcomprises: a stator provided with a positioning hole at one end of saidstepped yoke member; and a base equipped with a fastening pin providedto engage it with said positioning hole.
 14. The rotary motor accordingto claim 10, wherein said rotary motor comprises: magnetic pole teethprovided on each yoke member; driving coils wound around said magneticpole teeth; and coil terminals starting from said driving coils, passingthrough a space between said stepped yoke member and said base, andleading to coil terminal lands provided on the surface of said base. 15.A stacked stator core, comprising; a first core member formed bystacking a prescribed number of magnetic materials and made up of aplurality of yoke members connected to one another through a bendablebent portion; a second core member formed by stacking the prescribednumber of magnetic materials and made up of a yoke member arranged insuch a manner that one end of each magnetic material of said second coremember is successively connected to the other end of said first coremember through a bendable bent portion from the next magnetic materialof the other end of said first core member by shifting entirely saidsecond core member downwards; a third core member formed by stacking theprescribed number of magnetic materials, each of which is made up of thesame number of yoke members as said first core member connected throughthe bendable bent portion, and one end of the magnetic material of saidthird core member is connected to the other end of said core memberthrough a bendable bent portion by shifting entirely said third coremember downwards; and a fourth core member formed by stacking theprescribed number of magnetic materials and made up of a yoke memberarranged in such a manner that one end of each magnetic material of saidfourth core member is successively connected to the next stage of theother end of said third core member through a bendable bent portion fromthe next magnetic material of the other end of said third core member byshifting entirely said fourth core member downwards, with left the samenumber of stages of one end of said fourth core member unconnected asthe prescribed number of sages; wherein the first, the second, the thirdand the fourth core members are continuously arranged in a shape of aspiral; wherein the third core is stacked on the first core and theforth core is stacked on the second core.
 16. A rotary motor,comprising; a stator core having a plurality of yoke members made up ofa prescribed number of stacked sheet magnetic materials, a bendable bentportion provided between said yoke members, some part of said yokemembers are respectively shifted from adjacent yoke members in thestacking direction of said sheet magnetic materials; a stator formed bybending said stator core in a ring and connected both ends of saidstator core; and a base equipped with said stator.
 17. A stacked statorcore comprising; (N) yokes arranged spirally, each yoke having Lmagnetic materials and connected continuously to each other through bentportions, wherein the p+n-th yoke is shifted from the p-th yoke Lmagnetic materials in the stacking direction of said sheet magneticmaterials, wherein the p+n-th yoke is stacked on the p-th yoke, whereinN is the total number of yokes in the stacked stator core, L is thenumber of layers of magnetic materials, p is an integer greater than 0and n is the number of sides of the stacked stator core.